Histological study of the ependyma of the hypothalamic third ventricle in the water snake Natrix maura (L).

The ependyma of the hypothalamic third ventricle of Natrix maura (L) has been investigated by light microscopy employing Nissl and Golgi stains. Electron microscopy was also used. Brains were fixed by intraventricular perfusion and embedded in paraffin, celloidin and Spurr resin. Light-microscopically the ependyma appears as a simple layer epithelium with round or enlarged nuclei. It sometimes shows basal processes extending into the subependymal tissue. These processes can be clearly seen in Richardson stained semithin sections. They often contact the subependymal capillaries. Electronmicroscopically, tanycytes contacting capillaries show numerous microvilli and few cilia as well as pinocytotic vesicles at their apical surfaces. There are zonulae adherentes and probably gap junctions as well as digitations and desmosomes. In the apical cytoplasm there are mainly mitochondria, endoplasmic reticulum and Golgi apparatus. Near the nuclei and specially in the basal process there are many microtubules. The tanycytes contact the capillaries by an end foot containing mitochondria and pinocytotic vesicles, which are also observed in the endothelian cytoplasm. These structures lead us to think, like several other authors, that the tanycytes of Natrix maura (L) may serve as a linkage between CSF and the capillaries and that they possess the morphological features which are necessary to effect intracellular transportation.